function calculateEbaySTR() {
var activeInput = document.getElementById('activeListings').value;
var soldInput = document.getElementById('soldListings').value;
var resultContainer = document.getElementById('resultContainer');
var strResult = document.getElementById('strResult');
var ratioResult = document.getElementById('ratioResult');
var verdictBox = document.getElementById('verdictBox');
// Validation
if (activeInput === "" || soldInput === "") {
alert("Please enter both Active and Sold listing numbers.");
return;
}
var active = parseFloat(activeInput);
var sold = parseFloat(soldInput);
if (isNaN(active) || isNaN(sold)) {
alert("Please enter valid numbers.");
return;
}
if (active = 100) {
verdictText = "Excellent! High demand. This item sells faster than it is listed.";
verdictClass = "verdict-good";
} else if (str >= 40) {
verdictText = "Good. Healthy market with consistent sales.";
verdictClass = "verdict-good"; // Still green/good
} else if (str >= 15) {
verdictText = "Moderate. Long-tail item. Expect a slower sale.";
verdictClass = "verdict-ok";
} else {
verdictText = "Poor. Oversaturated market or low demand. High risk of unsold inventory.";
verdictClass = "verdict-bad";
}
verdictBox.className = "verdict-box " + verdictClass;
verdictBox.innerHTML = verdictText;
}
How to Calculate Sell-Through Rate on eBay
The eBay Sell-Through Rate (STR) is the single most important metric for resellers, flippers, and e-commerce managers. It measures the velocity at which an item sells relative to how many are currently available. Unlike simple profit margins, the STR tells you how fast an item will sell, helping you avoid "death piles" of stagnant inventory.
The Formula
While there are different ways retailers calculate sell-through, the standard formula used by eBay resellers for product research is:
This calculation is typically performed using data from the last 90 days (eBay's standard "Sold" history window).
Step-by-Step Guide to Finding the Numbers
To use the calculator above, you need to find two specific numbers on the eBay search page:
Search for your item: Type the specific model, brand, or description into the eBay search bar (e.g., "Sony VCR SLV-D380P").
Find Active Listings: Look at the number of results returned. This is your Active Listings number (the competition).
Find Sold Listings: Scroll down the left-hand sidebar filter menu and check the box that says "Sold Items". The number of results will change. This new number is your Sold Listings (the demand).
Interpreting Your Results
Once you have your percentage, here is how to decide whether to buy or list the item:
100% or Higher: This is a "Unicorn" or "BOLO" (Be On The Lookout). It means there are more buyers than sellers. If you price it competitively, it should sell within days.
40% to 99%: A very healthy item. These items generally sell within 1 to 4 weeks.
10% to 39%: A "Long Tail" item. It will likely sell eventually, but be prepared to store it for a few months. Only buy these if the profit margin is very high to justify the storage space.
Below 10%: A slow mover. Unless this is an extremely rare, high-dollar vintage item, it is often best to avoid these as the market is saturated.
Why Not Use the Retail Formula?
Traditional retail stores calculate sell-through as Sold / (Active + Sold). However, on eBay, inventory is dynamic. Resellers prefer the Sold / Active method because it provides a direct ratio of Demand vs. Supply. A 100% STR in reselling terms means for every 1 item listed, 1 item has sold, indicating a perfectly balanced market.